The archbishop began his mass with an appeal for peace and unity

Cardinal Malcolm Ranjith, the archbishop of Colombo, at his residence in the Sri Lankan capital. Jack Moore / The National

Sri Lanka's Roman Catholic leader on Sunday condemned the Easter attacks as "an insult to humanity" as the country marked a week since suicide bombers hit three churches and three luxury hotels.

The Archbishop of Colombo, Cardinal Malcolm Ranjith, held a private mass shown live on television after cancelling all public services amid fears of a repeat of the attacks which left 253 dead.

But a heavily guarded vigil was held outside St Anthony's Shrine in Colombo at 8.45am, the moment the bomber struck the church last week, killing dozens of worshippers.

The archbishop began his mass with an appeal for peace and unity in the multi-ethnic South Asian which has been put on edge by the attacks which also left nearly 500 injured.

"What happened last Sunday is a great tragedy, an insult to humanity," the cardinal said, urging followers to show kindness to others as a sign of respect for all the victims.

"Today during this mass we are paying attention to last Sunday's tragedy and we try to understand it. We pray that those who lost their lives that day have eternal life through the Lord and those who were injured will be healed soon.